1995 850 turbo wagon here. Ours does the exact same thing. Our AC is fully charged, but after driving for a little while, suddenly the air will blow warm. But that's not the weird part...

Weird part #1: When it starts to blow warm, if I turn the blower switch to "0" position, the residual air coming out of the vents is ice cold. As soon as I turn the fan back on to any position, the air starts out cold, then immediately turns warm again. I can hear some kind of slow steady clicking sound coming from behind the control unit. This is also a random thing.

Weird part #2: If I turn off the fan to the "0" position, sometimes the compressor will continue to turn. Sometimes it won't.

This is all really pissing me off. Let's not even mention that I have to recharge the bloody thing every month.

Looking for help.

kevin